Hi well loved 2005 VW sharan 1.9 TDi, was driving fine, parked up at shops, came back and no lights or dials on dash when I turn the key except door open light, and won’t fire, turns over no problem. Towed back to house, checked battery, checked fuses, new relay 109 still no joy!!! Seams like no ECU com/no fuel pump? Could it be the immobiliser? Tried disconnecting battery and shorting red and  black wires still nothing. Now the alarm goes off when I reattach the battery!! Anyone else had this or know what the problem might be???? Please help 😢

If the battery is definitely in good condition and charge is sufficient then I would look at immobiliser next
It would help to get hold of a scan tool to see what codes are present and particularly any relating to the immobiliser
Check the battery earth leads condition going to the chassis and engine/gearbox
Let us know how you get on with it